Xruns And Ardour: its the plugins!

[Robin]

Hi everyone,
Still concerning the problem I am having with Ardour and Jack, I have
made some progress: The Xruns occur when I have active LAPSDA plugins on
audio tacks. (I wanted to use a compressor and EQ per track).
 Is there something I can do about this?
 Have I missed a setting somewhere?
All help or suggestions are welcome.
Cheers,
Robin